Typhoon/Tempest, why the tubeframe?

[Bozothenutter]

Why do these two look like they have a tube frame cockpit section , while the rest of the aircraft actually seems to be a monocoque?

Almost looks like they put a Hurricane in there......

[fishplanebeer]

I'm no expert on these types but as a guess I would say it had something to do with Hawker's established and proven methods, allied to strength and ease of production to maximise output. After all it's a lot easier and quicker to design and build something if you can incorporate and utilise as many elements as possible of what you've done before. Saves you having to completely reinvent the wheel!

 

Regards

Colin.

[MDriskill]

I'm no expert either, but strongly suspect comrade fishplanebeer is on the right track.
 

Remember also that the design was developed pretty quickly (further incentive to stick with the tried-and-true), and was originally designed for two different engines requiring changes in the airframe (the Vulture-engined Tornado prototypes had a taller nose, lowered wing, and other differences from the Typhoon). I would think this would be easier to accomplish with the steel tube frame. 

Edited September 3, 2021 by MDriskill

[Troy Smith]

39 minutes ago, Bozothenutter said:

Almost looks like they put a Hurricane in there......

as @fishplanebeer says, build on established ideas.  Hawker were fairly conservative, and built on existing techniques.   the Typhoon/Tornado were on the drawing board in 1937, before the Hurricane had entered service,  the Tempest is basically a Typhoon fuselage with a new wing.... the Sea Fury is a Tempest wing with a new fuselage.... 

[Bozothenutter]

Evolutionary design then.

Building a monocoque, then stuffing in scaffolding, seems a bit belt AND braces though.

But it WAS a damn strong aircraft I suppose.

[Troy Smith]

1 hour ago, Bozothenutter said:

Evolutionary design then.

Building a monocoque, then stuffing in scaffolding, seems a bit belt AND braces though.

But it WAS a damn strong aircraft I suppose.

it was only the cockpit/forward fuselage/engine that was built like this, and this has the advantage of allowing most of the skinning in these areas to be removable, making maintenance a lot easier.  I'm not sure how much of the Hurricane construction carried over,  but I presume a fair amount, and this was tried and tested, and understood by ground crews.  

 

This image of the Typhoon at Hendon shows what I mean, 

 

the Fuselage behind the cockpit  was conventional monocoque.   

 

cheers

T

[dogsbody]

Doesn't that tubular construction go back to the Fury biplane? 

 

 

Chris

[jccorea]

1 hour ago, dogsbody said:

Doesn't that tubular construction go back to the Fury biplane? 

 

 

Chris

Indeed it does, via the Hurricane which used the same construction methods. Actually, skin over frame construction was easier to implement on the production line, and needed simpler tooling and jigs than monocoque. 

[elger]

Somewhat related, here's a video made by some folks building a Hawker Typhoon about the tubular structure. Goes from giving background information to going into really awesome detail

 

 

[Graham Boak]

I don't know how many if any parts were actually taken from the Hurricane, other than the principles and the method of production  Sir Sidney Camm developed this before the Fury and it was standardised throughout the Hawker Siddeley Group which was bad luck on the Gloster draughtsmen and designers who had just been retrained in Gloster's own new method.  Only to have to train again on monocoques.  

[gingerbob]

13 hours ago, Bozothenutter said:

Almost looks like they put a Hurricane in there......

 

Funny you should say that- check out these comparisons (first post) on my short-lived (and still "on hold") WiP:

 

 

Edit: this now makes me wonder which came first- the Typhoon/Tornado project, or the "all metal" wing for the Hurricane?

Edited September 4, 2021 by gingerbob

[EwenS]

1 hour ago, gingerbob said:

 

Edit: this now makes me wonder which came first- the Typhoon/Tornado project, or the "all metal" wing for the Hurricane?

 

Interesting question indeed.

 

Hurricane produced starting late 1937 and metal wings introduced on last 170 aircraft of the first batch in 1939, delivery of which was completed on 6 Oct 1939.

 

AM Spec F.18/37 which led to the Tornado/Typhoon issued to Hawker 15 Jan 1938. But Camm had already had some discussions with the AM in 1937 about the next generation fighter for which the engines were anticipated to be 60% heavier than the Merlin. First Tornado prototype flown on 6 Oct 1939 and first Typhoon prototype 24 Feb 1940.

 

So both projects seem contemporaneous to me.

[Geoffrey Sinclair]

Now all people have to do is define what is the start.  The change over to Hawker using stressed skin wings involved three related aircraft, Hurricane, Henley and Hotspur, with the Hurricane by choice third.  The Tornado and Typhoon came later.

 

February 1935 Hurricane prototype order, K5083, Specification F.36/34 Operational requirement 16.
10-Jul-35 Investigation into the construction of metal stressed skin outer wings commenced.
Apr-37 Experimental metal wing of Hawker type.  R.A.E. tests successful.
December 1937 Hurricane production begun.
Apr-39 Flight Tests of Hurricane I L1877 with metal stressed skin wings.

 

The Contract Cards report N2426, the 86th aircraft of the second order from Hawker was the last to be delivered with fabric wings (until some in mid 1940), taken on charge 14 November 1939.  A number of the L serial aircraft are marked as having metal wings, the "prototype" L1877 (332nd aircraft in the order), next is L2026 to 2028 (481st to 483rd aircraft in the order) and interestingly two of these were sold to Turkey.

 

Henley prototype order in 1935, K5115, Specification F.9/35 Operational requirement 20.
10 March 1937 Henley prototype first flight with fabric wings.
20 August 1937 Henley prototype first flight with metal wings
October 1938 Henley production begun.

 

Hotspur prototype order in 1935, K8309, Specification P.4/34 Operational requirement 13.  The Defiant prototype was K8310.
Also had stressed skin wings, lower priority project
14 June 1938, Hotspur prototype first flight, never brought up to operational standard.

 

Hawker did some design work on a fighter using the Vulture or Sabre in 1937. The P5219, P5224 Tornado/ P5212, P5216 Typhoon prototypes contract was issued in 1938 based on specification F.18/37, Operational requirement 51, by which stage it was understood the wings would be metal stressed skin.

 

Initial Production orders
L1547 - L2146 Hawker Hurricane I, 600 from Hawker, contract 527112/36
L3243 - L3642 Hawker Henley TT.III, 400    from Gloster, contract 540805/36
L3643 - L4031 Hawker Hotspur, 389 from A.V. Roe, contract 527115/36

R7936 / R8197 Hawker Tornado, 200 from A.V. Roe, contract 12148/39
R8198 / R8231 Hawker Typhoon IA/IB, 15 from Hawker, contract 12148/39
R8630 / R8981 Hawker Typhoon IB, 250 from Gloster, contract 12148/39

 

Notes from the "Hurricane Biography"

"Although production of the Hurricane was not unduly delayed there were nevertheless some important technical difficulties which had to be overcome after production had commenced.  The chief of these were the difficulty of discovering a way of correcting the dangerous tendency of the Hurricane in a spin; the setbacks encountered over the development of the stressed skin all metal wing and the alterations necessitated by the installing of a Merlin II engine instead of a Merlin I.  Fortunately these problems were of such a nature that the type could be used in service before modifications were incorporated in the production line.  Because of this, early deliveries were not prejudiced but the Hurricane had not, strictly speaking, completed its development until they were overcome."

 

"As regards the second difficulty, that of the stressed skin all metal wing (File No. 522507/36), the prototype had fabric wings, but it had always been hoped that production aircraft would have the new stressed skin wings.  In these wings the metal covering was made a part of the weight bearing aerial structure.  The importance if the stressed skin lay in its weight saving capacity.  Fabric covered wings had already reached the limit of weight allowed and the stressed skin wings saved no less than 70 pounds.  Investigations by the firms into this question had been started as early as July 1935.  When the production specification was drawn up however it was decided that the Hurricane should in the first place be fitted with fabric covered wings, which would be interchangeable with metal ones.  At this stage the technical state of the stressed skin wings was still experimental and not progressed further than the design stage.  The position was aggravated by the fact that Hawkers were working on two other monoplanes for the Air Ministry at the same time, the P.4/34 [Henley] and the F.9/35 [Hotspur], both of which were expected to have metal wings.  The construction was the same in each case, the difference being in the armament.  In June 1936 it was estimated that the test wing would be ready by September but "stiffness" problems arose which involved a new design and it was necessary to earmark a special group of men in the drawing office for metal wing development.  In December it was agreed that the P.4/34 should be fitted with the first pair of metal wings.  This decision naturally reacted adversely on the Hurricane and in October 1937 it was considered that the new wings could not come in before the 301st aircraft.  It was not until March 1939 that the first pair of production stressed skin wings were received from Glosters and fitted to production aircraft at Brooklands.  Shortly afterwards flight tests were completed and the wings were cleared for operational use."

 

Tempest II, Centaurus V engine, 8,915 pounds tare weight, 41 feet wingspan, length 34 feet 5 inches.
Sea Fury XI, Centaurus XII or XV engine, 9,240 pounds tare weight, 38 feet 4.75 inch wingspan, length 34 feet 8 inches.
So a changed fuselage and a shortened wing centre section.

 

A question, any WWII design actually have monocoque around the engine, versus a skin over the rather strong structure needed to support the weight of the engine, having the advantage of being able to totally remove the panels for access?

[dov]

The tubular sections:

From production easy, cheap, and to handle from low skilled workers. I do not knoe exactly, I assume that GB also lacked skilled workforce at this time! You can use welding robots of the early designs too.

This was done in Germany to incooperate Russian prisoner of wars.

The production has to be taken in account.

 

Higher technical ideas, had to wait at this time.

 

Happy modelling 

[Graham Boak]

Not really, the very specific methods used by Hawker required individual tools and skilled workers.   The tubes had squared ends, and their production was was one cause of the long delay before  Hurricanes became available as warbirds.  There was certainly not any consideration of welding, which was rare in the UK then.  Welding robots were just science fiction.

 

 

[Bozothenutter]

It would be enlightening to read about the 'subframe' from an engineering point of view. 

Does its presence mean the skin around the cockpit is/isn't structural?

A bit like Ferrari did with the F40, a tube frame, clad in carbon fibre that added to its stiffness.

[Jamie @ Sovereign Hobbies]

21 hours ago, Bozothenutter said:

Evolutionary design then.

Building a monocoque, then stuffing in scaffolding, seems a bit belt AND braces though.

But it WAS a damn strong aircraft I suppose.

 

Ah but it wasn't a monocoque in the slightest. Not until the Sea Fury did Hawker engineer a full monocoque fuselage. the tail end of the Typhoon and Tempest (largely similar) was a monocoque but that's the easy bit to stress analyse - without the 4 big point loads from the wing attachments and from the engine mounts.

 

It's a whole lot easier to perform stress analysis and member sizing on a pin-jointed tubular frame than it is on a monocoque structure so Hawker stuck with that for the difficult end of their aircraft and attached the eliptical cross section conical tube that was the aft fuselage at 4 simple-to-account for attachments on the spaceframe.

 

A pin jointed frame is 1st year university level stuff. Easy and predictable. Eventually though the attachments for the covering panels and the strength needed in the covering panels themselves mean that for increasingly faster aircraft it's better to accept the engineering pain and make the exterior skin earn its keep structurally.

[fishplanebeer]

From a complete novice's perspective I think the skins over the tubular frame were not structural/load bearing unlike the skins of the rear monocoque fuselage although clearly they would add external strength compared with say wood or fabric.

 

Regards

Colin.

[Bozothenutter]

Thanks @Jamie @ Sovereign Hobbies!

[dov]

Think also on production:

The tube cage as a subassembly group. Could be manufactured somewhere. By any factory, which is qualified.

The calculation was easier and perfect. The other way round, calculation was possible, but far away from perfect. 

Hawker did right so. I saw this cage with full installation. How easy and fast you can work so! Also you can control each cable and wire!

Today, at the F-15, at old days, the Japanese Shinden, is designed like this.

How to maintain a cockpit? You safe lots of hours with Hawker's designs.

Happy modelling 

[Jamie @ Sovereign Hobbies]

28 minutes ago, fishplanebeer said:

From a complete novice's perspective I think the skins over the tubular frame were not structural/load bearing unlike the skins of the rear monocoque fuselage although clearly they would add external strength compared with say wood or fabric.

 

Regards

Colin.

 

With structures in general I find it easiest to try to follow the Load Paths. Where do the loads actually go? A big strong panel held on by 4 screws into 4 brackets is ultimately only as useful as the strength in the screws and brackets.

 

As to monocoques and why Hawker shied away for a while, consider a coke can. By holding each end and twisting it's strong in torsion and by bending you'll find the thin tube pretty good with bending loads too. Point loads are a killer for monocoques though and need really special attention. Consider now supporting the coke can half-way along on two fingertips. Now make the load bigger - the thin skin buckles where the point loads go in. All the weight of the aircraft fuselage including the engine and everything inside the fuselage, multiplied by the maximum G limit, finds its way onto the wings at the points where the wing spars are pinned or bolted onto the fuselage. This is almost always included within a a big beefy fuselage frame or two, but this still makes for a significant change in stiffness of your coke can in one (or two) places and the skins don't like that because the usually imperceptible displacements all the metal undergoes suffers a steep gradient where these attachments are.

 

It's all resolvable, but the maths is much harder and without computers is ultimately impossible without making simplifications of some magnitude. Where simplifications are made to allow something to be described mathematically for hand calculation on paper, usually what goes with that is the structure is made bigger, thicker and therefore heavier to err on the safe side so it doesn't fall apart. Every time you make something heavier than it absolutely needs to be, you shave a bit off the aircraft's payload, service ceiling, acceleration, maximum speed and range. Make more simplifications than the enemy Engineers and your aircraft might just end up inferior.

[Space Ranger]

The Meyers 200 (U.S. civil aircraft) was of similar construction, with a steel tube central portion (cabin and inner wings) and monocoque outer wings, aft fuselage, and tail surfaces. They were essentially hand built, and after Aero Commander acquired the design, they concluded, after producing a few as the Aero Commander 200, they could not manufacture the airplane at a reasonable cost and make a profit.

Edited September 4, 2021 by Space Ranger

[FinnAndersen]

2 hours ago, fishplanebeer said:

From a complete novice's perspective I think the skins over the tubular frame were not structural/load bearing unlike the skins of the rear monocoque fuselage although clearly they would add external strength compared with say wood or fabric.

 

Regards

Colin.

Being an engineer myself, albeit a shipbuilding one, I'd say that there's no way to guess how to build a ship or an airplane. It's much more complicated and involve very advanced mathematics usually taught at universities. You also need to know how to design in a way that your (highly skilled) worker can produce items that goes into subassemblies and ultimately into the plane or ship. This involves knowing what tolerances are allowable so that the right and left wing actually is of equal length, to give an example.

 

Over the years this has been helped by computers, but these were not even ideas when Hawkers and Supermarine and the others designed cutting edge airplanes so that Britain could take up the fight against a very dangerous enemy.

 

We should be very grateful for these few people that was able let a very larger group of pilots win a decisive battle. Try to imagine BoB fought with Gloster Gladiators against 109's.

 

To other posters: I deeply grateful that you let me share your often unlimited knowledge. Please continue to do so and educate us all.

 

/Finn